Low Density Poly Ethylene (LDPE) is produced in an autoclave and/or tubular reactor at high pressure and temperature. High pressure, free-radical polymerizations are disclosed in the following references: U.S. Pat. Nos. 8,445,606, 4,135,044, 7,582,709, and JP050534422 (Abstract). The tubular process is preferred over the autoclave process by its capability to increase conversion by abstracting polymerization heat through cooling from the tubular reaction and cooling sections. However, it would be desirable to combine the higher conversion potential of a tubular process with the product capability of an autoclave process. Another parameter of importance is the polymer output of a high pressure polymerization process, which can range from 40 to 450 KTA or higher. The polymer output of a high pressure tubular process is affected by conversion level and monomer throughput. The conversion is governed by the desired products properties of the polymers to be produced. The monomer throughput depends on the design and the operating conditions of a secondary compressor system, which compresses the monomer feed stream to the required reactor inlet pressure.
Another parameter of importance is the energy required to produce a unit of high pressure polyethylene polymer. This energy requirement is largely determined by the compression energy required by the secondary compressor system. Thus, there is a need to maximize polymer production through increasing conversion level for a given amount of compression energy and/or to use less compression energy for compression the monomer reactor feed stream by reducing the reactor inlet pressure. The requirements on maximizing polymer output, extending product capability and/or reducing energy requirement have been met by the following invention.